414 BOWEN. 



of the cells. The formation of two different kinds of spermatozoa 

 (eupyrene and apyrene) in Lepidoptera has long been known, and a 

 somewhat different case (eupyrene and oligopyrene sperms) in certain 

 (prosobranch) molluscs is equally familiar. (See especially Meves 

 '03.) Less well known cases have been reported by Holmgren ('01) 

 and Voinov ('02) in Coleoptera. According to the former, in Staphy- 

 linus there are two kinds of primary spermatocytes which originally 

 differ greatly in volume, but at the time of maturation are of equal 

 size. The resulting sperms are likewise all of equal size, but according 

 to Holmgren, even though they resemble each other completely, on 

 the basis of their genetic inequality they must also be morphologically 

 and physiologically unequal. This case is of particular interest be- 

 cause, as is evident, the conditions are exactly the reverse of those in 

 the Hemiptera {Pentatomidac). According to Voinov, in Cybister 

 there are two kinds of spermatogenesis giving rise to sperms of differ- 

 ent morphological value. The two processes in this case are distinct, 

 occurring at different seasons of the year. Finally, in Rana, two sizes 

 of cells have long been known to occur in the gonads of many of the 

 larvae, the larger cells having been interpreted as abortive eggs. 

 The large spermatocytes of Arvelius might, indeed, easily be inter- 

 preted in a similar way, were it not for their further history and en- 

 vironment. Swingle ('21) has recently suggested that the two sizes 

 of cells are in reality two generations of spermatocytes, an interpreta- 

 tion which falls in line with the other cases noted above. It is possible 

 that all of these cases are really only scattered instances of a wide- 

 spread tendency toward polymorphism in sperm cells and are perhaps 

 ultimately to be explained on grounds more or less remotely similar. 

 In any event, the phylogenetic explanation offered by Swingle seems 

 less probable in the light of the other facts which I have here assembled. 

 There is, in all these cases, the common characteristic that the 

 phenomena peculiar to each seem to be perfectly normal and constant 

 for the particular species involved. Whether the sperms thus formed 

 are all able to function in any of the processes of normal fertilization 

 is not clear. It is indeed certain that they do not in the Anura, and 

 probably also in the case of the apyrene sperm of Lepidoptera in 

 which the nucleus is lacking. Whether the polymegalous sperms of 

 Hemiptera are of equal value in fertilization is not known, and the 

 cAddence for their retention in the seminal receptacle of the female 

 after copulation is not conclusive. The matter would be well worth 

 settling, for it would throw a most interesting side-light on the ques- 

 tion of the relative value of nuclear and cytoplasmic contributions in 

 fertilization. 



